His best known song was the 1965 Schlager "Marmor, Stein und Eisen bricht" (lit. "Marble, Stone and Iron Break") which sold over one million copies, and was awarded a golden record.

19-year-old Deutscher had ad-libbed the tune during an October 1965 audition at Musikverlag Edition Intro Gebrüder Meisel GmbH by humming the melody and only singing the characteristic chorus line of "Dum-Dum, Dum-dum"; asked by present songwriter Christian Bruhn what he intended to do with it to turn it into a complete song, he replied, "Det machst du! ("I want you guys to take care of it for me!"), so songwriter Günter Loose subsequently wrote the German lyrics to the melody.

In the US, the song was released in 1966 under the title Marble breaks and iron bends with English lyrics sung by Deutscher. This English version entered the Billboard Hot 100 in May 1966, peaking at # 80, and sparking a number of English cover versions by contemporary acts such as The Deejays (under the title Dum Dum (Marble Breaks and Iron Bends)), as well as by the two Australian acts Peter Fenton and Toni & Royce (aka Toni McCann and Royce Nicholas), none of which seem to have charted. The song later featured in the 2006 film Beerfest, during the Oktoberfest scene.